Public Short Ratio (PSR), also known as non-member short ratio, can be a helpful indicator to trade stock markets. It is used by many traders to find trading opportunities and to predict market movements. Public short ratio is defined as the ratio between public short selling number and total short selling number.

PSR = Total public short sells/total short sells.

The PSR ratio is disclosed by markets on a daily basis. High PSR values shows that the public are more bearish and low PSR values shows the public are more bullish. Although the ratio itself is an easy-to-use indicator, most traders use this ratio as a 10 day moving average. This makes interpretations easier and offer better flexibility. 25{97d7b09b4c5ca7df148cfec2d9ffc16c846b547c54009c0fb04b068da127cf4c} of moving average is taken as the crossing point. When ever the 10-day moving average is above 25{97d7b09b4c5ca7df148cfec2d9ffc16c846b547c54009c0fb04b068da127cf4c}, the market is considered bullish and when ever the moving average is below 25{97d7b09b4c5ca7df148cfec2d9ffc16c846b547c54009c0fb04b068da127cf4c}, the market is considered bearish. The more the ratio stays above/below the 25{97d7b09b4c5ca7df148cfec2d9ffc16c846b547c54009c0fb04b068da127cf4c} level, the more the chance of market reversal.

The basic idea behind public short ratio is public or retail traders are the worst short sellers; when compared to institutional traders and exchange member short sellers. So it is a good strategy to buy whenever public short and sell whenever go. Although sounds awkward the strategy has a high success history, especially for swing traders and long-term traders.

Advantages of public short ratio include 1) its is simple and easy-to-use, 2) has a good success history, 3) it is suitable for most traders, 4) offer better results when combined with other indicators, 5) has support available in most trading platforms and 6) is scalable with user demands.

Disadvantages of PSR include 1) it is less effective of short-term traders like day traders, 2) there is a good amount of risk associated with it, 3) the strategy does not work always as there can be situations where public are right, 4) the strategy may not work in high-volatile markets and 5) is not so suited for novice traders, especially who are not certain about minimizing their downside risks and hedging their positions.